1. Field of the Invention
This invention relates to a lens selection device, and more particularly relates to a lens selection device suited for use in reproducing apparatus (e.g., an electrostatic photocopier) wherein a plurality of discrete magnification lenses are shifted perpendicular to a respective reference axis to vary the magnification of an image to be reproduced.
2. Discussion of the Prior Art
In general, various types of variable magnification devices for use in a reproducing apparatus are known. These include (1) a device in which a mirror and a lens are shifted; (2) a device in which a conversion lens is used to vary magnification of an image; (3) a device in which a zoom lens is used; and (4) a device in which a plurality of individual magnification lenses are arranged in serial fashion and shifted together to select a desired magnification.
These known devices present the following drawbacks, however. With the first-mentioned device, it is necessary to shift the mirror and lens. This renders the mechanism complicated. Should lens aberration deviate from a predetermined value, a balance between spherical aberration and astigmatism may not be maintained or there may result an increase in coma aberration. With the second-mentioned device, magnification chromatic aberration tends to arise as astigmatism increases. As to the third-mentioned device, a continuous zoom lens is costly, and if a step zoom lens is used, there result difficulties in control. As to the fourth-mentioned device, unlike the other devices, it is simple in mechanism and poses no problem with lens aberration, as each lens is suited for its intended magnification. This fourth device presents a problem, however, in that when three lenses are used they require a space large enough to arrange five lenses in a direction perpendicular to an optical axis--this being impractical when space available to accommodate the lenses in the reproducing apparatus is limited.